Hitherto, C1 carbon sources have been cyanide ions (or hydrocyanic acid), carbon monoxide, phosgene and so forth. These materials are, however, highly toxic. Therefore, an alternative chemical material has been desired. Carbon dioxide is a renewable C1 carbon source. However, carbon dioxide is low-reactive and thus, its applications have been limited.
Cyclic carbonates have been extensively used as an electrolyte for a lithium-ion secondary battery, a raw material for polycarbonates, a polar aprotic solvent or the like. Cyclic carbonates have been typically produced by a method using a 1,2-diol and phosgene as starting materials. Such a method has had the problems of the use of highly toxic phosgene and byproduction of corrosive hydrogen chloride gas over the years. In contrast, a synthetic process for producing a cyclic carbonate by coupling carbon dioxide with an epoxide is a very clean process associated with no byproducts. There have been described some catalysts which promote the reaction.
Non-patent Reference 1 has described a process for manufacturing a cyclic carbonate using a porphyrin complex with Cr as a central metal as a catalyst and N,N-dimethyl-4-aminopyridine (hereinafter, sometimes abbreviated as“DMAP”) or N-methylimidazole as a co-catalyst. However, in this process, a reaction must be conducted under a high pressure of 5 MPa or more, resulting in difficulty in practical use.
Non-patent Reference 2 has described a process for manufacturing a cyclic carbonate using a porphyrin complex with Co as a central metal as a catalyst and DMAP, pyridine, N-methylimidazole, tricyclohexylphosphine oxide or triphenylphosphine as a co-catalyst. However, a reaction yield is sometimes low in the process. Using dichloromethane as a solvent, the process is environmentally unsound.
Non-patent Reference 3 has described a process for manufacturing a cyclic carbonate using a porphyrin complex or phthalocyanine complex with Cu as a central metal as a catalyst and DMAP as a co-catalyst. However, a reaction yield is sometimes low in the process. Using dichloromethane as a solvent, the process is environmentally unsound.
Non-patent Reference 4 has described a process for manufacturing a porphyrin complex with Co, Fe, Ru or Mn as a central metal and phenyltrimethylammonium tribromide (hereinafter, sometimes abbreviated as “PTAT”), tetrabutylammonium bromide or DMAP as a co-catalyst. However, a reaction yield is sometimes low in the process.
Non-patent Reference 5 has described a process for manufacturing a cyclic carbonate using a porphyrin complex with Mg as a central metal as a catalyst and triethylamine as a co-catalyst. However, a reaction yield is sometimes low in the process.